The chemical compositions and bioactivities of ether extracts of an endophytic fungus Paecilomyces sp. isolated from Panax ginseng were reported, and the comparative analysis of the constituents, antifungal and antitumor properties of the ether extracts from this fungus and its host ginseng were also conducted. By means of GC/MS technique, 51 compounds of Panax ginseng and 38 compounds of Paecilomyce sp. were determined. It is attractive that the extracts derived from Paecilomyce sp. and ginseng samples contained the same compound falcarinol, a natural pesticide and anti-cancer agent. The ether extracts of Paecilomyce sp., tested at 7.8 microg/ml, completely inhibited the visible growth of Pyricularia oryzae. Furthermore, both extracts were tested against four human pathogenic fungi and showed the IC(80) of Paecilomyce sp. was 4 microg/ml against Trichophyton rubrum, equally to the control. Finally, the in vitro antitumor experience showed that the most of the IC(50) values were all being below 20 microg/ml.